In an internal combustion engine, for example, an engine of an automobile, a plurality of spark plugs for respective cylinders is required to generate ignition sparks at predetermined time points. Therefore, an integrated coil supporting unit is employed so as to send ignition signals to respective ignition coils corresponding to the spark plugs.
In general, the integrated coil supporting unit includes an elongated casing and a plurality of coil units, which project from the casing in parallel. Each coil unit includes the ignition coil and is plugged into a corresponding one of plug receiving holes, which are formed in an engine block at predetermined pitches. The spark plug is installed at the bottom of each plug receiving hole, and each coil unit is connected to the corresponding spark plug. However, the integrated coil supporting unit, which is made by means of resin molding, is likely to be deformed after molded, so pitches among the coil units tend to vary. Accordingly, the integrated coil supporting unit generally has a structure, in which each coil unit is supported in the casing slidably in its radial direction.
For example, the above integrated coil supporting unit is shown in FIGS. 7A to 7D (JP-A-H9-250437). The integrated coil supporting unit has a connector block 100, the shape of which is platy and elongated, a plurality of connector supports 103, which are disposed on the connector block 100 at predetermined intervals, and a plurality of coil connectors 112, each of which is disposed on the corresponding connector support 112. As shown in FIG. 7C, each connector support 103 has an inlet hole 105, locking tongues 106, which are formed around the inner periphery of the inlet hole 105, a support main body 104, which has bolt holes 108, and a cylindrical wall 107, which projects downward from the support main body 104.
As shown in FIG. 7D, the coil connector 112 includes a contact portion 115, which contacts the support main body 104, a concave portion 116, a cylindrical insert portion 113, which is inlet in the inlet hole 105, and a lockable tab 114, which is locked by the locking tongues 106. At the bottom of the concave portion 116, an electrically conductive bus bar 117 is embedded. An electrically conductive terminal 118, exposed to the surface of the connector support 103, is connected to one end of the bus bar 117. Moreover, the other end of the bus bar 117 is connected to an electrically conductive terminal 119.
As shown in FIG. 7D, the coil connector 112 is engaged with the connector support 103. The coil connector 112 covers the connector support 103, and the terminal 119 is electrically connected to an ignition coil 125. In a state where the lockable tab 114 is locked by the locking tongues 106, the coil connector 112 can be slid in its radial direction on the connector support 103 with the locking tongues 106 deformed.
However, in the integrated coil supporting unit, the connector support 103 and the coil connector 112 respectively have complicated structures. Accordingly, mold tools for molding the connector supports 103 and the coil connectors 112 are required to be complicated, so the manufacturing cost is high.
Moreover, since the locking tongues 106 and the lockable tab 114 are formed thin, they are likely to be broken. Further, the ignition coil 125 is supported only by the insert portion 113. Accordingly, when the ignition coil 125 is vibrated by the engine, the ignition coil 125 and the connector support 103 are likely to be disconnected, or the insert portion 113 is likely to be broken.